Neuronal intercellular communication occurs through specific synaptic membrane domains and is mediated by the action of neurotransmitter receptor-effector complexes. We propose to develop affinity isolation strategies to isolate neuronal synaptic membrane domains from Drosophila and rat central nervous system using modified Alpha-bungarotoxin as an affinity ligand. Alpha-Bungarotoxin-horseradish peroxidase covalent complexes or biotin labeled Alpha-bungarotoxin will be bound to the neuronal membrane population containing their receptors. These membranes will then be isolated by subsequent interaction with Sepharose CL6B derivatized with anti-peroxidase antibodies or avidin and avidin derivatives or similarly derivatized small latex beads. Synaptic membranes will be characterized morphologically by transmission electron microscopy and cytochemically with Alpha-bungarotoxin-horseradish peroxidase conjugates. In addition, isolated synaptic domains will be analyzed for neurotransmitter receptor ligand binding sites ([3H]quinclidinylbenzilate, [125I]Alpha-bungarotoxin, etc.) as well as gel electrophoresis protein patterns and enzyme activity. Alpha-Bungarotoxin-receptor function will be studied by combined physiological and binding studies in Aplysia californica, tissue culture cells and rat superior cervical sympathetic ganglia. Changes in chloride ion conductance will be monitored by intracellular recording and 36C1- flux measurements, characterized pharmacologically and correlated with [125I]Alpha-bungarotoxin binding, [3H]nicotine and [3H]d-tubocurarine binding. These studies may result in an identification of the functional nature of neuronal Alpha-bungarotoxin binding sites as well as provide insight into the molecular organization of neurotransmitter recognition, transduction, and effector domains of neurotransmitter receptor-effector complexes.